Method and apparatus for the production of elongated conical metallic articles

ABSTRACT

Conical metallic blanks for the production of progressive helical springs are produced by rotating an elongated metallic rod about its axis, by simultaneously moving a die with three equidistant idler rolls in axial direction of the revolving workpiece, and by moving the rolls toward the axis of the workpiece in accordance with a predetermined pattern so that the rolls convert the workpiece into a blank which tapers from one end toward the other end, either gradually or stepwise. The means for moving the rolls toward the axis of the workpiece comprises a fixed template and a scanning arm whose follower tracks the template and which transmits motion to the rolls by way of a turnable ring and pivotable one-armed levers.

[451 Sept. 26, 1972 [54] METHOD AND APPARATUS FOR THE PRODUCTION OF ELONGATED CONICAL METALLIC ARTICLES [72] Inventor: Otto Oehm, Werdohl, Germany [73] Assignee: Stahlwerke Bruninghaus Gesellschaft Mit, Westhofen/Westfalen, Germany [22] Filed: May 22, 1969 [21] Appl. No.: 826,943

[52] US. Cl. ..72/107, 72/81, 72/377 [51] Int. Cl. ..B2ld 15/00 [58] Field of Search ..72/7,95, 100,121,81, 107, 72/110, 377

[56] References Cited UNITED STATES PATENTS 1,913,711 6/1933 Kamp ..72/95 X 2,367,612 1/1945 Reed ..72/100 3,019,678 2/1962 Le Fiell ..72/7 3,195,331 7/1965 Curtis ..72/7 3,071,992 1/1963 Martin ..72/7 3,149,511 9/1964 Warren ..72/95 Primary Examiner-Charles W. Lanham Assistant ExaminerMichael J. Keenan AttorneyMichael S. Striker I [57] ABSTRACT Conical metallic blanks for the production of progressive helical springs are produced by rotating an elongated metallic rod about its axis, by simultaneously moving a die with three equidistant idler rolls in axial direction of the revolving workpiece, and by moving the rolls toward the axis of the workpiece in accordance with a predetermined pattern so that the rolls convert the workpiece into a blank which tapers from one end toward the other end, either gradually or stepwise. Thevmeans for moving the rolls toward the axis of the workpiece comprises a fixed template and a scanning arm whose follower tracks the template and which transmits motion to the rolls by way of a turnable ring and pivotable one-armedlevers.

3 Claims, 3 Drawing Figures PA TENTED 3,693,390

sum 3 OF 3 Inventororro Q50 METHOD AND APPARATUS FOR THE PRODUCTION OF ELONGATED CONICAL METALLIC ARTICLES BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for the production of elongated metallic articles, particularly for the production of blanks which can be utilized in the manufacture of so-called progressive helical springs. Still more particularly, the invention relates to a method and apparatus for conversion of elongated metallic rods of constant diameter into elongated blanks which taper from one end toward the other end.

Recent types'of automotive vehicles often employ progressive helical springs, i.e., springs wherein the diameter decreases from one end toward the other end. At the present time, such springs are obtained by coiling of metallic blanks whichtaper from one end toward the other end, and the blanks are customarily produced by turning of metallic rods with templates, milling, grinding and/or hammering. Such methods of producing tapered blanks are quite expensive, especially since the rods must be machined with a high degree of'precision and the blanks must have a very satisfactory surface finish. Furthermore, when the blanks are produced by a material removing method, such as milling or turning, the losses in valuable material (usually high-quality spring steel) are considerable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel and improved method of converting elongated rod-shaped metallic workpieces into blanks, which taper from one end toward the other end, in a materialand time-saving operation.

Another object of the invention is to provide a method according to which a large series or a smaller batch of tapered (conical) blanks can be produced in such a way that the dimensions of any given blank are identical with those of each other blank.

A further object of the invention is to'provide an apparatus which can be utilized in the practice of the above outlined method and which is capable of producing tapered blanks from different types of metallic workpieces and of producing different types ,of blanks from identical or different workpieces.

Still another object of the invention is to provide a novel die for use in the above outlined apparatus.

One feature of my invention resides in the provision of a method of converting rod-shaped elongated metallic workpieces of at least substantially constant diameter into blanks each of which tapers in a direction from one end toward the other end. The method comprises the steps of subjecting a workpiece to what can be termed a drawing or stretch rolling action, and intensifying the drawing action in a direction from the one toward the other end of the workpiece. In accordance with a presently preferred embodiment, the method comprises the step of rotating the workpiece about its axis in the course of the drawing or stretch rolling action. The latter can be carried out in two or more successive stages.

If the intensifying step is gradual, the diameter of the resulting blank decreases gradually (i.e., constantly) in a direction from one end toward the other end of the blank. If the intensifying step includes effecting gradual reduction of at least two axially spaced sections of the workpiece and effecting a steeper reduction in the diameter of the section between such axially spaced sections, the resulting blank is provided with a more or less pronounced shoulder between the two axially spaced sections.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary transverse sectional view of an apparatus which embodies one form of the invention, substantially as seen in the direction of arrows from the line [-1 of FIG. 2, with the workpiece omitted;

FIG. 2 is a plan view of the structure shown in FIG. 1, with a portion of the supporting means for the die broken away; and I FIG. 3 is a sectional view substantially as seen in the direction of arrows from the line III-III of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing in detail, there is shown an apparatus which can convert elongated metallic rodshaped workpieces 1 into blanks or semifinished products which taper from one end toward the other end. The apparatus comprises a die 3 which includes three or more preferably equidistant drawing" members in the form of rolls 2 each of which is rotatable about its own axis. The rolls 2 define a passage 23 for the workpiece 1 and are movable toward and away from the axis of the die 3; such axis is normal to the plane of FIG. 1 and coincides with the axis of the workpiece I, as viewed in FIG. 2. The ends of the workpiece l are held by and clamped in supporting means which includes two supporting members 20 (one shown in FIG. 2). These supporting members 20 can constitute the headstock and the tailstock of a lathe and are rotatable about the axis of the workpiece 1 whereby the latter shares such rotary movement. One of the supporting members 20 is preferably movable in the axial direction of the workpiece to compensate for elongation or draft which takes place during treatment. At least one of the supporting members 20 is fixedly mounted in the frame of the lathe to hold the corresponding end portion of the workpiece 1 against axial movement during conversion into a tapered blank. The supporting means for the die 3 comprises a carriage 21 which is mounted on suitable ways (not shown) of the lathe in such a way that the axis of the die 3 coincides with the axis of the properly held workpiece 1. The drive means for moving the carriage 21 in the direction of the axis of the workpiece 1 (i,e., in axial direction of the die 3) comprises a cable 22 which is coupled to the carriage and can move it in a direction to the left, as viewed in FIG. 2. 'A second drive means is provided to rotate the workpiece 1 about its axis; such drive means includes a gear or pulley 24 (indicated in FIG. 2 by phantom lines) which can rotate the workpiece 1 with or relative to the adjoining supporting member 20.

The apparatus further comprises displacing means for moving the rolls 2 toward the axis of the die 3 at a predetermined rate in response to movement of the carriage 21 in axial direction of the workpiece l. The displacing means comprises a suitable template 5 which is tracked by the roller follower 7 of a scanning arm 6. The rate at which the rolls 2 move toward each other in response to axial movement of the die 3 from the righthand end toward the left-hand end of the workpiece 1 (as viewed in FIG. 2) depends on the profile of the template 5, i.e., on the configuration of its surface 5 a, and on the position of the template with reference to the die 3. The illustrated template 5 has a straight surface 5 a so that the diameter of the blank which is obtained on treatment of the workpiece 1 decreases gradually from the right-hand end toward the left-hand end of the blank, as viewed in FIG. 2. However, it is clear that the template 5 can be replaced with a template whose surface comprises two or more axially spaced straight portions and slightly or strongly inclined intermediate portions between such axially spaced portions sothat the blank then comprises axially spaced gradually tapering sections and at least one steeply or gradually sloping intermediate section which defines a more or less pronounced shoulder. Furthermore, depending on the desired conicity of the blank, on the hardness of the material of the workpiece 1, on the sturdiness of the apparatus and/or certain other factors, the blank can be obtained in a two-stage, three-stage, etc. operation, i.e., the carriage 21 is then caused to advance the die 3 repeatedly in axial direction of the same workpiece; during each such pass, the rolls 2 reduce the diameters of successive increments of the workpiece to an extent which is determined by configuration and/or positioning of the template which is utilized in the respective stage of the operation.

FIG. 3 shows that the axes of shafts 8 for the rolls 2 make an acute angle and are arranged askew with respect to the axis of the die 3. The rolls 2 rotate on radial bearings 9 (here shown as needle bearings) and are held against axial movement on shafts 8 by thrust bearings 10. The shafts 8 are mounted in discrete onearmed follower levers 13 each of which has a pivot pin mounted in an inner ring 12 and each of which has a suitably configurated convex follower portion 26. The scanning arm 6 is rigid with an outer ring 11 which constitutes a triple cam and has three concave internal cam faces 14 each cooperating with one of the follower portions 26. It will be readily understood that the rolls 2 move toward the axis of the die 3 when the scanning arm 6 is pivoted in a clockwise direction, as viewed in FIG. 2. Suitable springs (not shown) are provided to bias the follower portions 26 against the respective cam faces 14 and to bias the roller follower 7 against the surface 5 a of the template 5.

When the apparatus is in use, the gear or pulley 24 rotates the workpiece l which is held by the supporting members 20. The cable 22 moves the carriage 21 in axial direction of the workpiece 1 whereby the rolls 2 rotate about their axes in response to engagement with the peripheral surface of the rotating workpiece. The carriage 21 entrains the arm 6 whose roller follower 7 tracks the surface 5 a ofthe template 5 whereby the rolls 2 advance toward the axis of the die 3 and automatically reduce the diameters of successive increments of the workpiece l in accordance with the desired schedule.

An important advantage of the improved method and apparatus is that the workpieces 1 can be converted into tapered blanks within short periods of time, in a fully automatic way or semiautomatically, with a high degree of reproducibility, and without any (or without appreciable) waste in metallic material. This is particularly important when the material is spring steel. The surface finish of blanks is exceptionally satisfactory, especially if the workpiece l is converted into a blank in two or more stages.

In accordance with a more specific feature of the present invention, the roller follower 7 is mounted on the outer end portion of the scanning arm 6 by means of a suitable swivel bearing 7 a which permits the follower to wobble or swivel in order to compensate for eventual misalignment of its groove 7 b with the surface 5 a of the template 5. In this way, that portion of the groove 7 b which receives the adjacent part of the surface 5 a can move toward or away from the axis of the die 3 within limits determined by the swivel bearing 7 a The peripheral surfaces of the rolls 2 are preferably rounded (see particularly FIG. 3) to insure more satisfactory deformation of successive increments of the workpiece 1 when the carriage 21 moves to the left, as viewed in FIG. 2. Similar results can be obtained by employing conical rolls. Such conical or convex rolls can be used with advantage even if the axes of the shafts 8 are not inclined with reference to the axis of the die 3. The rate at which the rolls 2 move toward the axis of the die 3 while the latter travels axially of the workpiece 1 also depends on the configuration of faces 14 on the outer ring 11; such faces are preferably rounded, inclined and/or curved in such a way that they effect gradual inward movement of rolls 2 in response to angular displacement of the ring 11 at a constant speed.

It is clear that the improved apparatus is susceptible of many modifications without departing from the spirit of the present invention. For example, the die 3 can rotate with reference to the workpiece l which is then held against rotation or rotates at a different speed or counter to the direction of rotation of the die. Also, the die 3 can support more than three rolls and the movements of rolls 2 toward and/ or away from the axis of the die 3 can be effected by mechanisms which do not necessarily employ a template. Furthermore, the apparatus can be equipped with two or more dies and with a requisite number of supporting, driving and displacing means so that it can treat two or more workpieces at a time. If the apparatus comprises two or more dies, all of the dies can be operatively connected with a'common template or each die can cooperate with a separate template.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

I claim:

1. A method of producing solid metal rods having an axis and a diameter which continuously changes in axial direction of the rod from cylindrical metal rods, comprising the steps of rotating the cylindrical rod about its axis; engaging the outer surface of said rod with surfaces of three rolls circumferentially displaced about the rod axis and having each an axis askew to the axis of said rod and a convexly curved peripheral surface so that said rolls form a roll pass coaxial with the rod axis while each of said rolls is in substantially point engagement with the rod; moving said rolls together in axial direction of said rod while continuously changing the cross-section of said roll pass in dependence on the movement of the rolls in axial direction of said rod to thereby continuously change the diameter of said rod by stretch rolling in which the rod material is caused to flow in axial direction of said rod.

2. A method as defined in claim 1, wherein the cross section of said roll pass is continuously reduced in dependence on the movement of said roll in axial direction of said rod to thereby continuously reduce the diameter of said rod so as to produce from said cylindrical metal rod a rod tapering toward one end.

3. A method as defined in claim 2, wherein said stretch-rolling step includes effecting gradual reduction of diameters of at least two axially spaced sections of the rod and steeply reducing the diameter of the section between such axially spaced sections. 

1. A method of producing solid metal rods having an axis and a diameter which continuously changes in axial direction of the rod from cylindrical metal rods, comprising the steps of rotating the cylindrical rod about its axis; engaging the outer surface of said rod with surfaces of three rolls circumferentially displaced about the rod axis and having each an axis askew to the axis of said rod and a convexly curved peripheral surface so that said rolls form a roll pass coaxial with the rod axis while each of said rolls is in substantially point engagement with the rod; moving said rolls together in axial direction of said rod while continuously changing the cross-section of said roll pass in dependence on the movement of the rolls in axial direction of said rod to thereby continuously change the diameter of said rod by stretch rolling in which the rod material is caused to flow in axial direction of said rod.
 2. A method as defined in claim 1, wherein the cross section of said roll pass is continuously reduced in dependence on the movement of said roll in axial direction of said rod to thereby continuously reduce the diameter of saiD rod so as to produce from said cylindrical metal rod a rod tapering toward one end.
 3. A method as defined in claim 2, wherein said stretch-rolling step includes effecting gradual reduction of diameters of at least two axially spaced sections of the rod and steeply reducing the diameter of the section between such axially spaced sections. 